Clock Synchronisation in Stationary and Accelerated Frames

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In summary: So according to your own clock, the two clocks are out-of-sync. Now let's say I take a second rocket and I place it next to the first rocket. In your frame the clock on the second rocket is moving away from you, and the clock on the first rocket is moving towards you. So according to your own clock, the two clocks are now in-sync. But according to the clock on the second rocket, the clock on the first rocket is still out-of-sync. So in general, if I have two clocks that I want to synchronize in a moving frame of reference, I need to find a way to synchronize them using
  • #1
rab99
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if 2 clocks are synchronised in a stationary frame of refernece and then that frame of ref is accelerated up to a constant velocity will the clocks still be synchronised ?
 
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  • #2
Welcome to PF!

rab99 said:
if 2 clocks are synchronised in a stationary frame of refernece and then that frame of ref is accelerated up to a constant velocity will the clocks still be synchronised ?

Danger said:
If both of them remain in the same frame, then the answer should be 'yes'. I'm no expert on Relativity, though. It's probably best to wait for a real scientist to weigh in with some answers for you.

Hi rab99! Welcome to PF! :smile:

Yes, if they're attached to a spaceship, say, and the spaceship accelerates, and then stops accelerating, the clocks should still be synchronised. :smile:
 
  • #3
A lot depends on the method of acceleration method used. Born rigid acceleration (keeping the separation between the the nose and the tail of the rocket at the appropriate length contracted length) and bell acceleration (keeping the separation of the nose and tail constant in the non accelerating frame) will result in the clock going out of syncronisation. See https://www.physicsforums.com/showthread.php?t=216113
 
  • #4
kev said:
A lot depends on the method of acceleration method used. Born rigid acceleration (keeping the separation between the the nose and the tail of the rocket at the appropriate length contracted length) and bell acceleration (keeping the separation of the nose and tail constant in the non accelerating frame) will result in the clock going out of syncronisation. See https://www.physicsforums.com/showthread.php?t=216113

Nice work.

I didn't realize that it could go out of sync under born-rigid acceleration.
 
  • #5
Thanks for the reply

It is a little unclear from your explanation but I interpret it that both Bell and Born cause the clocks to become unsynchronised.

From examining the thread that you referred me to if:
all the appropriate parameters are measured, by the appropriate measuring device, in the appropriate frame, Then the clocks can be adjusted (say by moving the hands on the clock) to allow for the amount they became unsychronised, during the acceleration, to make them synchronised again yeh ?

Of course at a constant velocity contraction is constant and time is constant

I guess the question I want answered is , is it possible to have two clocks perfectly synchronised in a moving frame of reference yes or no? I suspect the answer is yes
 
  • #6
I need to clarify my last post a little

From examining the thread that you referred me to if:
all the appropriate parameters are measured, by the appropriate measuring device, in the appropriate frame, Then the clocks, ONCE THEY ARE AT A CONSTANT VELOCITY, can be adjusted (say by moving the hands on the clock) to allow for the amount they became unsychronised, during the acceleration, to make them synchronised again yeh ?



AND


I guess the question I want answered is , is it possible to have two clocks perfectly synchronised in a CONSTANT VELOCITY moving frame of reference yes or no? I suspect the answer is yes
 
  • #7
rab99 said:
I need to clarify my last post a little

From examining the thread that you referred me to if:
all the appropriate parameters are measured, by the appropriate measuring device, in the appropriate frame, Then the clocks, ONCE THEY ARE AT A CONSTANT VELOCITY, can be adjusted (say by moving the hands on the clock) to allow for the amount they became unsychronised, during the acceleration, to make them synchronised again yeh ?



AND


I guess the question I want answered is , is it possible to have two clocks perfectly synchronised in a CONSTANT VELOCITY moving frame of reference yes or no? I suspect the answer is yes
Well, do you understand about the relativity of simultaneity in relativity which says that different frames define what it means for clocks to be "synchronized" differently? In relativity, if I'm moving inertially and I have two clocks at rest relative to me, I synchronize them in my frame using the "Einstein synchronization convention" which is based on assuming that light moves at the same speed in all directions in my own frame--so, for example, I can set off a flash at the midpoint of the two clocks, and then as long as they both read the same time at the moment the light from the flash hits them, I define them to be "synchronized" in my frame. But it's not hard to see that if each observer synchronizes their own clocks this way, they will say that the clocks of other observers are out-of-sync. For example, say I'm on a rocket which is moving forward in your frame, and I synchronize clocks at the front and back of the rocket by setting off a flash at the midpoint and setting the two clocks to read the same time when the light reaches them. In your frame the clock at the front of the rocket is moving away from the point in space where the flash was set off, while the clock at the back of the rocket is moving towards that point, so naturally if you assume the light moves at the same speed in both directions in your frame, that means the light will actually hit the clock at the back before it hits the clock at the front, so if both clocks read the same time when the light hits them that must the two clocks are out-of-sync in your frame.

So, the short answer to your question is, yes, whenever two clocks are moving at constant velocity it is always possible to synchronize them in their own rest frame using the Einstein synchronization convention, but this will result in the clocks being out-of-sync in the frame of other observers moving at constant velocity who see the clocks moving relative to themselves.
 
  • #8
So assuming I have an observer within the same frame as the clocks and I have an observer external to that frame (or in a different frame) it is entirely possible thru measurement and adjustment to synchronise the clocks so the observer within the frame will say they are synchronised

and

thru measurement and further adjustment to synchronise the clocks so the observer external to the frame will say they are synchronised

Of course the adjustment for the external observer will be different than the adjustment required for the internal observer

and

of course it is impossible to adjust the clocks so they are simutaneously synchronised for both the internal and external observer if the internal and external observer are in different frames ie frames traveling at a different velocity or direction relative to to each other ... is this correct ?
 
  • #9
rab99 said:
So assuming I have an observer within the same frame as the clocks and I have an observer external to that frame (or in a different frame) it is entirely possible thru measurement and adjustment to synchronise the clocks so the observer within the frame will say they are synchronised

and

thru measurement and further adjustment to synchronise the clocks so the observer external to the frame will say they are synchronised

Of course the adjustment for the external observer will be different than the adjustment required for the internal observer

and

of course it is impossible to adjust the clocks so they are simutaneously synchronised for both the internal and external observer if the internal and external observer are in different frames ie frames traveling at a different velocity or direction relative to to each other ... is this correct ?
A "frame" is just a coordinate system, it isn't localized to a particular region of space, so I don't see what you mean when you distinguish "external to the frame" and "in a different frame". But other than that I'd say your correct, it's possible to adjust the clocks so they're synchronized in the rest frame of an observer who sees the clocks as being at rest relative to himself, or it's possible to adjust them so they're synchronized in the rest frame of an observer a different observer who sees the clocks in motion relative to herself, but not both (except in the special case where the observer who sees the clocks in motion sees them moving exactly perpendicular to the axis between the two clocks).
 
  • #10
I always think of a frame as being a space ship. One person is standing on the ground observing the spaceship moving and there is a person in the space ship. If the clocks are in the spaceship then the pseron in the spaceship is at rest relative to the clocks the person on the ground is not at rest relative. I guess the inside the spaceship is a regoin of space that is a moving frame as opposed to the air just outside the skin of the spaceship or the person on the ground?

The main thing is it is possible thru measurement and adjustment to make two clocks synchronised wrt any observer, regardless of the frame that they happen to be in
 
  • #11
rab99 said:
I always think of a frame as being a space ship. One person is standing on the ground observing the spaceship moving and there is a person in the space ship. If the clocks are in the spaceship then the pseron in the spaceship is at rest relative to the clocks the person on the ground is not at rest relative. I guess the inside the spaceship is a regoin of space that is a moving frame as opposed to the air just outside the skin of the spaceship or the person on the ground?
No, you're thinking of "frame" incorrectly. A frame is a coordinate system that fills all of space and time, which may be infinite. When physicists talk about the ship's frame, all that means is a coordinate system in which the ship is at rest--i.e. its coordinate position does not change with the passage of coordinate time in that system. A frame is not localized to any particular region of space.
rab99 said:
The main thing is it is possible thru measurement and adjustment to make two clocks synchronised wrt any observer, regardless of the frame that they happen to be in
Clocks are not "in" one frame or another, since every frame covers every region of space, including whatever region the clock is occupying. But yes, any pair of clocks can be synchronized in any frame.
 
  • #12
If there is one coordinate system for the moving spaceship and there is separate coordinate system for the person standing stationary on the ground is there a corordinate system common to both?

surely there must be as space is continuous

Are coordinate systems just a mathematical construct used to make it easier to visualise reality ?
 
  • #13
… why are there no mathematicians at the North pole … ?

rab99 said:
Are coordinate systems just a mathematical construct used to make it easier to visualise reality ?

Yes!

Don't get confused between mathematics and reality! :smile:

Mathematicians can define anything they like, to make calculation easier!

For example, there's a mathematical singularity at the North pole (of the Earth) … but physicists know there's no singularity there! :smile:
 
  • #14
rab99 said:
If there is one coordinate system for the moving spaceship and there is separate coordinate system for the person standing stationary on the ground is there a corordinate system common to both?

surely there must be as space is continuous

Are coordinate systems just a mathematical construct used to make it easier to visualise reality ?
I think you're still misunderstanding something here--both coordinate systems include the moving ship, and both coordinate systems include the person on the ground. The only difference is that in one coordinate system the person on the ground is at rest and the ship is in motion, while in the other coordinate system the ship is at rest and the person on the ground is moving.
 
  • #15
Oh Ok I understand one coordinate system reflects the perspective of the person on the ground and the other coord system reflects the perspectice of the person in the space ship. I knew that things often had to be considered from both perspectives but thanks for clarifying how this is explained mathematically.
 

1. What is clock synchronisation in stationary and accelerated frames?

Clock synchronisation in stationary and accelerated frames is the process of ensuring that two or more clocks are displaying the same time, despite being in different frames of reference. This is important in relativity, as time can appear to pass differently depending on an observer's frame of reference.

2. Why is clock synchronisation important in science?

Clock synchronisation is important in science because it allows for accurate measurement and comparison of events across different frames of reference. It is essential for making precise calculations and observations in fields such as physics and astronomy.

3. How is clock synchronisation achieved in stationary frames?

In stationary frames, clock synchronisation is achieved by using a common reference frame, such as a universal time standard. This allows for the clocks to be set to the same time and stay in sync as long as they remain in the stationary frame.

4. What challenges arise in clock synchronisation in accelerated frames?

In accelerated frames, the challenge of clock synchronisation arises due to the effects of time dilation and gravitational time dilation. These effects cause time to appear to pass differently for observers in different frames, making it difficult to accurately synchronise clocks.

5. How is clock synchronisation addressed in special and general relativity?

In special relativity, clock synchronisation is addressed by using the Einstein synchronisation convention, which involves synchronising clocks at the same location in different frames. In general relativity, clock synchronisation is addressed by taking into account the effects of gravity on time, and using techniques such as gravitational time dilation to adjust for these effects.

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